The present application claims priority under 35 USC 119 to Japanese Patent Application No. 2001-069228 filed on Mar. 12, 2001.
1. Field of the Invention
The present invention relates to a Stirling engine having a thermoelectromagnetic generator associated with a heat regenerator for storing and radiating the heat of an operating gas which flows between an expansion chamber and a compression chamber.
2. Description of Background Art
Transactions (B) of the Japan Society of Mechanical Engineers, Vol. 62, No. 595, entitled xe2x80x9cIncreasing the Performance of a Semi-Free-Piston Stirling Engine Regenerator with a Compound Mesh Matrixxe2x80x9d describes increasing the performance of a heat regenerator to improve the thermal efficiency of a Stirling engine by using a laminated assembly of metal screens of different meshes, instead of a laminated assembly of metal screens of the same mesh which has heretofore been used in general, as a Stirling engine heat regenerator.
Since the operating gas flows back and forth through small passages provided by the metal meshes of the heat regenerator, the resistance presented to the flow of the operating gas by the metal meshes lowers the overall thermal efficiency of the Stirling engine. In view of the fact that the temperature of the heat regenerator periodically increases and decreases, it is proposed to combine a thermoelectromagnetic generator with the heat regenerator to generate electric power to compensate for the energy loss caused by the resistance presented to the flow of the operating gas.
The present invention has been made in view of the above drawbacks. It is an object of the present invention to generate electric power efficiently with a thermoelectromagnetic generator using the heat regenerator of a Stirling engine.
To achieve the above object, there is proposed according to the present invention a Stirling engine including a communication path interconnecting an expansion chamber heated by a heating unit and a compression chamber cooled by a cooling unit. A heat regenerator is disposed in the communication path for storing and radiating the heat of an operating gas which flows between the expansion chamber and the compression chamber. A thermoelectromagnetic generator is associated with the heat regenerator wherein the thermoelectromagnetic generator has a yoke providing a closed magnetic circuit passing through the heat regenerator, magnetomotive force means for supplying magnetic fluxes to the magnetic circuit, and an induction coil responsive to a change in the magnetic fluxes in the magnetic circuit. The heat regenerator is made of a ferromagnetic material and has a Curie temperature which is present in a range of varying temperatures of the heat regenerator.
With the above arrangement, since the temperature of the heat regenerator which is made of a ferromagnetic material varies periodically across the Curie temperature, the magnetic fluxes passing through the induction coil are varied greatly each time the temperature of the heat regenerator passes through the Curie temperature, generating a large electromotive force across the induction coil. Since the thermoelectromagnetic generator associated with the heat regenerator is capable of generating electric power efficiently, an energy loss caused by the resistance to the flow of the operating gas as it passes through the heat regenerator is compensated for thus increasing the overall thermal efficiency of the Stirling engine.
According to the present invention, the heat regenerator includes a plurality of segments divided in the direction in which the operating gas flows, the segments having respective Curie temperatures progressively lower from a side of the heat regenerator near the expansion chamber toward a side of the heat regenerator near the compression chamber.
With the above arrangement, because the heat regenerator is divided into a plurality of segments, and the Curie temperatures of the respective segments are progressively lower from the side of the heat regenerator near the expansion chamber towards the side of the heat regenerator near the compression chamber. Even if the temperature distribution of the heat regenerator is progressively lower from the side of the heating unit to the side of the cooling unit, the temperature of the entire area of the heat regenerator increases and decreases across the Curie temperature, allowing the thermoelectromagnetic generator to generate electric power efficiently.
Permanent magnets 32 in the embodiment correspond to the magnetomotive force means according to the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.